Bird ringing at Tophill Low
Last week saw the start of our bird ringing season here at the reserve. For the past eleven years Graham Scott has conducted a Constant Effort Site (CES) ringing scheme in an area of South Scrub.
The CES scheme,
co-ordinated by the British Trust for Ornithology starts on the 1st
May each year and runs till the end of August. During this time ringing days
are planned (weather permitting) every 10 days which equates to about 12
sessions. Here at Tophill, Graham has carried out this commitment each year with a team of ringers (except in 2020) and in doing so has ringed 1,673 birds, covering 35 species,
ranging from kingfishers to Cetti’s warblers.
The CES scheme has been running since 1983. Ringers use the
same nets in the same locations over the same time period at regular intervals
throughout the breeding season and this is carried out at 140 locations across
the UK. The aim of the scheme is to monitor a particular site to establish the
number and variety of species that are breeding in the area. It provides
valuable trend information on abundance of adults and juvenile productivity at
a particular site and also adult survival rates for 24 common songbird species.
Re traps give evidence that birds are staying within the targeted area year
on year and the number of each species ringed gives an overall picture of whether the numbers of certain species are
remaining constant or changing over the years. Re traps of adults ringed in
previous years are used to estimate survival rates. All this data adds into
other data sources such as the Breeding Bird Survey and other ringing schemes
co-ordinated by the BTO providing a detailed picture of bird populations.
The process of bird ringing is carried out by people who have been trained and hold a valid permit that is issued by the BTO. Birds can be caught by a variety of methods but the most common, and the one used at the reserve is by mist netting. This requires a very fine net, secured by poles that is placed within a certain area. Birds are unable to see the net, they then fly into it and are safely held in a pocket of netting before being carefully removed ready for processing. The process consists of identifying the species, noting its sex and age, recording its wing length and its weight. A tiny metal ring is then carefully secured around a leg, the specific number recorded before the bird is released. The metal ring is similar in weight proportionately to wearing a wristwatch, causing no adverse affect to the individual
Last Monday a total of 46 birds, of 17 species were caught
and ringed, 7 birds were re trapped birds; a good start to the survey this
year. Of the birds that had been re trapped; a reed warbler was first ringed in
Jun 2019, a willow warbler was ringed in August 2020, a robin was first ringed
in April 2019, a Cetti’s warbler had been ringed in June 2019 and a very long
lived long tailed tit was ringed as an adult bird at the reserve in June 2018.
Small passerines such as these species are known to be fairly short lived,
information such as this data adds to that evidence.
Today the ringing team were back, they caught less birds,
only 20 this morning as the weather wasn’t as ideal and will return on another
ten occasions throughout the breeding season.
Over the years (2010-2019) the scheme on the site has shown
that willow warbler and chiff chaff numbers have remained fairly constant, with
two poor years (2014, 2015). Sedge warblers have increased throughout the
period but have shown high fluctuations in numbers between years. Similarly
reed warbler numbers have increased. With both species this may be due to the
addition of a new net ride near some reeds but within the period that this ride
existed numbers have also increased. The fluctuation in numbers in recent years
is often due to ringing on days when passage birds appear to be moving through.
Blackcap numbers have remained fairly
constant with double figures ringed annually in most years.
Some notable recoveries (when the bird has been caught in a
different area to the CES site) have been a sedge warbler that was caught in Lesteven, France, a reed
warbler than was caught in Jersey, another two reed warblers were re trapped in
Sussesx. A blackcap has been recovered at Stanford reservoir in
Northamptonshire, a robin at Spurn and a long tailed tit travelling to
Flamborough head, East Yorkshire. Two birds that were caught at Tophill, yet
ringed elsewhere are both reed warblers, one ringed in Woumen, Belgium and one
ringed at Fishlake meadows in Hampshire.
The scheme will be up and running throughout the summer now
that rules have been relaxed and the ringing team are able to get back on site.
We will continue to keep everyone updated on this fascinating aspect to our
wildlife monitoring at the reserve. Our thanks go to Graham Scott and his ringing team for their efforts, in particular Will Scott who has provided all the ringing data records.
